The novel invention herein described relates to an apparatus useful in making highly weather resistant structure covering materials in situ, a method for using such an apparatus, and products made with such an apparatus. These covering materials are particularly useful as roofing layers. The conventional means to prepare roof covering materials have not included in situ preparation under high temperature conditions. When heated rollers have been used for sealing and fusing purposes, they have been used at temperatures below 400 degrees Centigrade.